Fibrosis is a crippling, largely irreversible, result in many chronic inflammatory diseases of the lung and other tissues. The modulating forces controlling the abundance and organization of collagen in the lung in disease states are only dimly understood at present. This investigation will analyze the effects of lymphocyte and monocyte mediators upon lung fibroblasts since these chronic inflammatory cells are found with such frequency in the vicinity of ongoing fibrosis. Purified human peripheral blood lymphocytes and monocytes are variously stimulated or incubated without stimulation, for the preparation of conditioned supernatants containing factors active in the modification of human fibroblast activities. Fibroblast monolayers are assayed by microscopy and by the use of various radioisotopic markers such as 3H-thymidine, 14C-proline and 3H-tryptophan to monitor viability and proliferation and to determine effects upon non-collagenous and collagenous protein synthesis and degradation. The contribution of various relative populations of mononuclear cell types, the effects of various immune and non-immunologic stimuli of these mononuclear cells, the effects of varying concentrations of the conditioned supernatants, and the isolation of active factors by standard analytical and biochemical separation techniques form the essence of the studies. Stimulatory factors of collagen synthesis are particularly under study. BIBLIOGRAPHIC REFERENCES: Johnson, R.L. and Ziff, M.: Lymphokine stimulation of collagen synthesis; J. Clin. Invest. 58: 240-252, 1976. Johnson, R.L.: Soluble factor(s) from human mononuclear cells enhance collagen synthesis by human lung fibroblasts; Fed. Proc. 36:1074, 1977 (Abstract).